In the phi phenomenon, for an exo deviation, the paddle motion direction when the eye is uncovered is which?

• A. Opposite direction
• B. Same direction
• C. No movement
• D. Vertical movement

Answer: (B)

In this context, the phi phenomenon used with the paddle test shows a directional motion that matches the actual movement of the deviated eye. For exotropia, the eye tends to drift outward to fixate. When that eye is uncovered, it moves outward, and the phi illusion presents the paddle as moving in the same horizontal direction as that outward drift. So the observed motion mirrors the eye’s outward movement rather than opposing it or staying still. If the misalignment were inward, you’d expect motion in the opposite direction; vertical deviations would produce vertical motion. Hence the paddle appears to move in the same direction as the exodeviation.